Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B25/00—Layered products comprising a layer of natural or synthetic rubber
  • B32B25/04—Layered products comprising a layer of natural or synthetic rubber comprising rubber as the main or only constituent of a layer, which is next to another layer of the same or of a different material
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J121/00—Adhesives based on unspecified rubbers
• • E—FIXED CONSTRUCTIONS
  • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
  • E01F—ADDITIONAL WORK, SUCH AS EQUIPPING ROADS OR THE CONSTRUCTION OF PLATFORMS, HELICOPTER LANDING STAGES, SIGNS, SNOW FENCES, OR THE LIKE
  • E01F9/00—Arrangement of road signs or traffic signals; Arrangements for enforcing caution
  • E01F9/50—Road surface markings; Kerbs or road edgings, specially adapted for alerting road users
  • E01F9/506—Road surface markings; Kerbs or road edgings, specially adapted for alerting road users characterised by the road surface marking material, e.g. comprising additives for improving friction or reflectivity; Methods of forming, installing or applying markings in, on or to road surfaces
  • E01F9/524—Reflecting elements specially adapted for incorporation in or application to road surface markings
• • E—FIXED CONSTRUCTIONS
  • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
  • E01F—ADDITIONAL WORK, SUCH AS EQUIPPING ROADS OR THE CONSTRUCTION OF PLATFORMS, HELICOPTER LANDING STAGES, SIGNS, SNOW FENCES, OR THE LIKE
  • E01F9/00—Arrangement of road signs or traffic signals; Arrangements for enforcing caution
  • E01F9/50—Road surface markings; Kerbs or road edgings, specially adapted for alerting road users
  • E01F9/576—Traffic lines
  • E01F9/578—Traffic lines consisting of preformed elements, e.g. tapes, block-type elements specially designed or arranged to make up a traffic line
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/554—Wear resistance
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
  • C08L2666/26—Natural polymers, natural resins or derivatives thereof according to C08L1/00 - C08L5/00, C08L89/00, C08L93/00, C08L97/00 or C08L99/00

Definitions

• the present invention relates to a pavement marking material which may be adhered to a roadway to provide traffic control markings and the like.
• Preformed pavement marking materials are used as traffic control markings for a variety of uses, such as short distance lane striping, stop bars, and pedestrian lane markings at cross walks and lane and shoulder delineators and skips on highways.
• preformed pavement marking materials comprise a continuous, preferably wear-resistant top layer overlying a flexible base sheet. Such marking materials are typically applied to road surfaces using pressure-sensitive adhesives or contact cement. Pavement markings such as markings for crosswalks, stop bars, etc. at intersections, sometimes referred to as "transverse applications", are subjected to veiy high, very quick shear forces from vehicles which start, stop, and turn at the location.
• the shear stresses encountered in transverse applications are typically substantially greater than the shear forces typically encountered due to traffic in "long line” or “longitudinal applications” such as lane and shoulder delineators and skips on highways.
• the adhesives on many markings do not provide desired shear resistance to achieve satisfactory performance in transverse applications.
• U.S. Patent No. 3,902,939 discloses a pavement marking tape material which utilizes an adhesive which is not tacky at room temperature but which is activated by a hot primer layer or solvent to provide adhesion to pavement surfaces.
• U.S. Patent No. 4,146,635 discloses a road marking tape material designed to better withstand tangential stresses internally by incorporation of an inextensible, tensionally resistant intermediate layer.
• U.S. Patent No. 2,956,904 discloses use of high energy electron (“e-beam”) bombardment of rubber resin type pressure-sensitive adhesives to increase the cohesive properties of the adhesives.
• the present invention provides an improved pavement marking material which comprises a top layer, optionally a flexible base sheet, and a layer of adhesive. Once applied to road surfaces, pavement marking materials of the invention exhibit exceptional impact shear resistance, thereby providing improved durability and safety.
• the adhesive layer of marking materials of the invention comprises a hereinafter described hydrocarbon-based elastomer, preferably an amorphous hydrocarbon elastomer using a solventless hot melt process, and an effective amount of hereinafter described tackifier, e.g., between about 80 and about 125 parts by weight of tackifier per 100 parts by weight of elastomer, i.e., between about 80 and about 125 phr of tackifier.
• Pavement marking materials of the invention are particularly well suited for use to mark crosswalks, stop bars, etc. at intersections, i.e., transverse applications. Pavement marking materials of the invention are also well suited for use in longitudinal applications, e.g., lane and shoulder delineators and skips, and may be used on a variety of pavement surfaces, e.g., concrete and asphalt.
• Figure 1 is a cross-sectional view of a portion of an illustrative embodiment of pavement marking material of the invention.
• This figure which is idealized, is not to scale and is intended to be merely illustrative and non-limiting.
• pavement marking material 10 comprises top layer 12, optional base sheet 14, and adhesive layer 16 which adheres marking material 10 to a substrate such as the pavement surface of a roadway (not shown).
• Adhesive layer 16 comprises rubber and tackifier and may vary in thickness from about 14-50 mils when applied commercially to a substrate.
• a preferred range of thickness of the adhesive layer is from about 20-27 mils, with a lower range preferred in southern climates and a higher range in northern climates.
• Rubbers used herein include those having a low glass transition temperature, i.e., a T g of between about -120 ° C and about -50°C.
• the rubbers can be lightly crosslinked (preferably by electron beam up to about 4 Mrads) but not to the point of insolubility in toluene.
• a small weight percentage of chemical crossiinking such as a phenolic resin may be used to increase molecular weight of the rubbers, as an alternative to electron beam.
• suitable elastomers include the following: natural rubber, polyisoprene, polybutadiene, polyisobutylene, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene monomer rubber (EPDM), poly(ethylene/butylene), poly(alpha-olefin) and styrene- butadiene random copolymer rubber. These may be used singly or in combination and are distinguished from block copolymer types.
• a preferred rubber is natural rubber.
• Tackifiers used in the present invention should be compatible with the rubber component, i.e., they are preferably substantially miscible in all proportions.
• Tackifiers used in the present invention preferably have a ring and ball softening point between about 70°C and about 140°C.
• suitable tackifiers include the following types: rosin and rosin derivatives, C5 and C 9 hydrocarbon resins, and terpenes and terpene phenolic derivatives. These may be used singly or in combination.
• a preferred tackifier which is completely miscible with natural rubber is ⁇ -pinene.
• Useful in the invention are pressure sensitive adhesives (PSAs) preferably produced by a process employing a continuous compounding device.
• a number of such devices are known. They may comprise a single unit or a series of units interconnected so as to continuously process the elastomer.
• the device has a sequence of alternating conveying and processing sections which are interconnected.
• An example of a continuous compounding device useful in the present invention is a twin screw extruder having a sequential series of conveying and processing zones.
• a plurality of input openings are preferably provided along the length of the extruder to facilitate the addition of various materials such as tackifier resins, fillers, antioxidants, plasticizing aids (if desired), radiation enhancers such as electron beam sensitizers and photoinitiators, light stabilizers and other adjuvants known in the art.
• a melt pump and filter may be present either as an integral part of the extruder, or as a separate unit to facilitate both the removal of the adhesive from the compounding device and the removal of unwanted contaminants from the adhesive stream.
• the elastomer is added to a first conveying zone of the compounding device at a controlled rate so that the elastomer does not completely fill the zone.
• the elastomer may be pelletized by grinding or extrusion pelletization prior to being fed to the compounding device. Alternately, it may be fed directly into the compounding device without grinding or pelletization using a device such as a Moriyama extruder. If the elastomer has been pelletized, it is preferably treated with a material such as talc to prevent agglomeration of the pellets.
• the elastomer is then transported by the first conveying zone to a first processing zone where it is masticated.
• the first processing zone typically is designed to be essentially completely full and to masticate the elastomer. Additionally, the processing zone conveys the elastomer to the next zone. It may be desirable to provide the first processing zone as at least two discrete processing sections separated from each other by a transporting section. This permits the elastomer to be masticated in steps, with cooling of the masticated elastomer between each step.
• elastomers may both be added to the first conveying zone and masticated in the first processing zone.
• the elastomers may be added sequentially to different conveying zones with sequential mastication after each elastomer addition. Sequential elastomer addition to different conveying zones may also be employed when a single elastomer is used.
• Mastication is preferably carried out in the absence of materials which will lubricate the elastomer and prevent reduction of its molecular weight. This does not however, preclude the presence of small amounts of such materials, provided that the amount present does not effectively reduce the rate of mastication.
• Certain other solid adjuvants such as talc, inorganic fillers, antioxidants, and the like, may be fed to the compounding device such that they are present during mastication.
• the masticated elastomer then passes from the first processing zone to a second conveying zone.
• the second conveying zone is not completely filled by the elastomer.
• Tackifier, and optionally other additives are fed to the second conveying zone.
• the resulting mixture is conveyed to the next processing zone where they are mixed to form a blend of the materials.
• a number of techniques may be used to feed these materials to the compounding device. For example, a constant rate feeder such as a K-Tron loss-in- weight feeder may be used to add solid materials. Heated pail unloaders, gear pumps, and other appropriate equipment for feeding liquids at a controlled rate may be used to feed the liquids to the compounding device.
• Additives present at low concentration may be pre-blended with one or more of the other components for more accurate addition. Although substantially all mastication occurs in the first processing zone, there may be some mastication which occurs in subsequent processing of the elastomer through the compounding device. This additional mastication may occur in subsequent conveying or processing zones. In any event, the degree to which the elastomer must be masticated in the practice of the invention varies with each elastomer employed and the finished product desired.
• the elastomer must be sufficiently masticated to (i) permit subsequently added tackifiers and any other adjuvants to be satisfactorily mixed into the elastomer to form a blend and (ii) to permit the blend to be extruded as a stream that is essentially free from both rubber particles and from visually identifiable regions of unmixed tackifier and any other adjuvants.
• the composition may now be referred to as an adhesive.
• This adhesive typically has a viscosity at the processing temperature in the range from 500 Poise to 5000 Poise (measured at a shear rate of 1000 sec "1 ). Higher viscosity adhesives may also be processed in the process of the invention.
• the processing temperature of the adhesive is typically in the range of 100-200°C.
• a twin screw extruder is preferably used as the compounding device.
• the extruder screw should be configured to masticate the elastomer in the first processing zone prior to addition of the tackifier.
• the first processing zone preferably allows mastication and blending of the elastomer components.
• the portion of the extruder and screw following the first processing zone must be designed to permit the addition of the tackifier and other additives to the elastomer and good mixing of the elastomer with these materials.
• the screw is designed so that a homogeneous adhesive composition results.
• the screw has a sequence of conveying and processing zones. Flow restriction and mixing elements are provided so as to achieve appropriate flow along the screw and obtain appropriate mastication and mixing.
• the conveying zones may contain ordinary Archimedes screw elements.
• the processing zones may contain kneading blocks, pin mixers, or other elements designed for mastication, compounding and mixing.
• Flow restriction elements such as kneading blocks arranged with a reverse pitch, reverse pitched conveying screws, a disk element or other device designed to restrict the flow of material, may also be present in the processing zone to ensure that the portion of the processing zone preceding these elements tends to run full of material while the conveying zone following them tends to run only partially full.
• the adhesive composition comprises between about 80 and about 125 phr of tackifier such that the adhesive has excellent impact shear resistance while maintaining sufficient degree of tack to adhere to a substrate.
• Adhesive compositions which contain insufficient amounts of tackifier typically tend to exhibit lower impact shear resistance and may tend to be displaced from the substrate upon multiple shearing impacts.
• Adhesive compositions which contain excessive amounts of tackifier typically tend to be more difficult to bond to a substrate and require use of a primer to overcome this difficulty. They also may be more likely to undergo brittle failure and pop off the substrate, especially at low temperatures.
• Optimum tackifier loading is dependent upon the softening point of tackifier; relatively low softening point tackifiers being less effective than relatively high softening point tackifiers in reinforcing the adhesive at equal tackifier loading levels.
• the portion of the adhesive layer which is to be applied to the substrate i.e., bottom portion of the adhesive, preferably has a Static Shear, determined according to the test described below, of less than about 2000 seconds.
• the surface to which a pavement marking of the invention is applied is preferably substantially dry to ensure effective bonding.
• top layer 12 or optional base sheet 14 should be selected such that they bond strongly enough together to resist delamination under conditions to which the pavement marking is exposed.
• Top layer 12 is typically a flexible polymeric layer which is preferably durable and wear-resistant.
• materials from which top layers may be made include polyvinyls, polyurethanes, epoxy resins, polyamides, polyureas, and polyesters. Mixtures of such materials may be used. Suitable polymeric materials may be either thermoplastic or thermosetting polymers.
• top layer 12 will also comprise a plurality of retroreflective particles 18 and/or skid-resistant particles 20 embedded in top layer 12 with some particles protruding from the top surface of top layer 12 as known to those skilled in the art.
• retroreflective particles 18 and/or skid-resistant particles 20 embedded in top layer 12 with some particles protruding from the top surface of top layer 12 as known to those skilled in the art.
• embodiments of the invention may be made with top layers containing skid-resistant particles as illustrated in U.S. Patent No. 3,935,365 (Eigenmann).
• retroreflective particles 18 which are suitable for use in pavement marking materials of the invention include glass microspheres having an index of refraction between about 1.5 and about 2.0, typically preferably between about 1.8 and about 1.95. Glass microspheres having an index of refraction closer to about 1.5 are typically less costly and more durable than those having higher indexes of refraction, whereas those having an index of refraction between about 1.8 and about 1.9 typically tend to provide high retroreflective efficiency. It will be understood by those skilled in the art that other embodiments of retroreflective particles 18 may be used in marking materials of the invention.
• Skid resistant particles 20 are preferably used to impart greater frictional properties to the marking material.
• skid resistant particles may be selected of proper type and sufficient quantity that the marking material has a skid resistance in the British Portable Skid Resistance Test of at least 50 BPN.
• BPN means the British Portable Number as measured using a Portable Skid Resistance Tester built by Road Research Laboratory, Crawthorne, Berkshire, England.
• White aluminum oxide granules are an illustrative example of suitable skid-resistance particles.
• Another illustrative example is ceramic spheroids that are a fired ceramic comprising a mineral paniculate, alumina, and a binder.
• particles 18 and 20 may be treated with a coupling agent that improves adhesion between particles 18 and 20 and the polymeric components of top layer 12.
• a coupling agent may be incorporated in the composition from which top layer 12 is formed.
• Coupling agents typically comprise an inorganophilic portion, which associates with particles 18 and 20, and an organophilic portion, which associates with the organic components of top layer 12.
• Silane compounds e.g., aminosilanes, are an illustrative example of typically suitable coupling agents.
• Optional base sheet 14 is typically between about 20 and about 50 mils (0.8 and 2 microns) thick to impart desired conformability and strength to marking material 10. If base sheet 14 is too thin, it may not provide sufficient strength or support for marking material 10 to enable material 10 to be handled and applied to a roadway. If base sheet 14 is too thick, resultant marking material 10 may tend to stick up so far from the pavement to which it is applied as to be too readily subject to damage or dislodgment by snowplows.
• Base sheet 14 and/or top layer 12 may also comprise paniculate fillers to lower the cost as well as modify the properties, e.g., reinforcement, surface hardness, flexibility, etc., of base sheet 14, top layer 12, and overall marking material 10.
• coloring agents such as pigments may be added to base sheet 14 and/or top layer 12 to impart desired coloration.
• suitable coloring agents include titanium dioxide pigment which provides white color and lead chromate pigment which provides yellow color.
• pavement markings may be made using adhesive layers as described herein with top layers presenting reflective elements as disclosed in U.S. Patent No. 3,587,415 (Eigenmann).
• pavement markings of the invention will be wound into roll form for storage with a suitable low adhesion backsizing or release agent applied to the top surface of the pavement marking backing before rolling.
• test methods were used. Unless otherwise indicated, the tests were performed at room temperature.
• Rolling Ball Tack was determined by allowing a clean stainless steel ball weighing about 8.35 grams and having a diameter of about 0.5 inch (1.2 centimeters) to roll down a ramp with a 20° slope from a total vertical height of about 2.1 inches (5.3 centimeters) onto a horizontal layer of the subject adhesive. The distance from the end of the ramp to where the ball came to a stop was measured and reported as Rolling Ball Tack. This procedure is similar to Pressure Sensitive Tape Council Test Method PSTC-6.
• Solvent Resistance was determined by immersing a 1 inch (2.5 centimeter) square piece of the subject adhesive on polyester backing in toluene for 24 hours. After the 24 hours period, the samples were evaluated and found soluble indicating that the adhesives were substantially uncrosslinked.
• Static Shear was determined by applying a 0.5 by 4 inch (1.2 by 10 centimeter) strip of a test tape comprising a 7 mil (25 micrometer) film of the subject adhesive on a 2 mil (50 micrometer) polyester terephthalate film to a stainless steel panel with a 0.5 by 0.5 inch (1.2 by 1.2 centimeter) portion of the tape in contact with the panel and the remainder extending beyond.
• the sample was laminated to the test panel by hand rolling with a 2 kilogram roller for six passes.
• the test panel was then suspended in a test stand at a 2° angle from vertical with the tape on the upper surface of the panel such that no gravity-induced peel force would be applied to the tape.
• Impact Shear Resistance was determined using a vehicle wear simulator designed to simulate shear and wear conditions experienced by a pavement marking located near an intersection.
• the simulator has a test area consisting of a horizontal annular ring about 6 feet (1.8 meters) in diameter and about 1 foot (0.3 meter) in width having an unprimed concrete surface.
• Samples of pavement marking material are cut into 2 by 6 inch (5 by 15 centimeter) rectangles and mounted in the annular ring with the long axis of the sample being aligned with the radial axis of the ring. Each sample is then rolled by hand with a rubber roller to provide good contact to the unprimed pavement surface and its initial position noted.
• the frame is rotated, driving the tires across the surface of the test area at 60 revolutions/minute which is equivalent to a lineal tire speed of about 12.5 miles hour (20 kilometers/hour), simulating the high impact shear and abrasion forces encountered at a highway intersection. Impact Shear Resistance was evaluated as the lateral movement of the sample on the substrate following a specified number of tire hits.
• Example 1 The following samples were prepared and tested using the above described tests in the laboratory to demonstrate the effect that tackifier has on impact shear properties and the effect of adhesive thickness on both resistance to impact type shear (VWS, Vehicle Wear Simulator) and physical property measurements (i.e., static shear and rolling ball tack).
• Natural rubber technical grade - SMRCV-60, (i.e., Standard)
• the tack (i.e., the ability to make a bond to a substrate with moderate pressure and short times) goes to zero. 4. In some borderline cases, some level of tack can be brought back by using thicker adhesive levels. (Sample 2.1 & 2.2 in table 1).
• Placement of the samples throughout the intersection was mapped out prior to installation to ensure that replicates of a particular formulation were evenly distributed throughout the various environments. For example: In a typical intersection, turn lanes are a more severe environment (due to higher shear levels encountered there) then straight thru lanes. If all the replicates of a particular formulation are placed in blocks that are just in straight thru lanes, then the sample may artificially appear good whereas in reality the formulation could perform poorly in a high shear environment.
• the following adhesive formulation was anaerobically compounded and coated out onto differential release liner.
• a controlled Mooney viscosity natural rubber (SMR CV60) (available from The Ore and Chemical Company, Inc.) was ground and dusted with talc. This rubber was fed to Zone 1 of a co-rotating twin screw extruder (ZSK-90 Werner- Pfeiderer Co.) at the rate of 124 lbs./hr. (56.3 kg/hr). The extruder screw operated at 250 rpm. The rubber was transported and masticated through Zones 3 and 4. PiccolyteTM S-l 15 tackifier was added to Zone 4 at the rate of 49.8 lbs/hr (22.6 kg/hr).
• Additional PiccolyteTM S-l 15 was added to Zone 5 at the rate of 74.6 lbs/hr (33.9 kg/hr).
• IrganoxTM 1010 was added with the tackifier stream at Zone 5 at the rate of 1.2 lbs/hr (.55 kg hr).
• the adhesive was metered to a 14 inch (35.6 cm) wide contact extrusion die with a rotating steel rod on the downstream side of the die gap to smear the adhesive onto the tight side of a differential release liner.
• the adhesive was applied at a rate of 250 lbs/hr (113.5 kg/hr) and coated to a width of approximately 14 inches (35.6 cm).
• the line speed was automatically adjusted to achieve a coating thickness of 20 mils (508 ⁇ m).
• the melt temperature was maintained at approximately 110°C throughout the extruder.
• the adhesive was exposed in line to electron beam radiation at a dose of 1 MRad using an accelerating potential of 210 kV.
• the resulting adhesive was laminated to N-420, a preformed lane marking material made by 3M.
• the resulting tape was found to be useful as a primerless intersection lane marking tape.
• Example 1 Using the process and materials described in Example 1, the following adhesive formulation was compounded and coated onto release liner for later lamination to a lane marking tape.
• Ground natural rubber was fed to Zone 1 of the extruder at a rate of 66.4 lbs/hr (30.1 kg/hr).
• Tackifier was added with the rubber stream into Zone 1 at the rate of 10 lbs/hr (4.5 kg/hr). Temperatures in Zones 1-3 were set to approximately 40°C.
• Tackifier was added to zone 4 at the rate of 19.9 lbs/hr (9.0 kg/hr). Additional tackifier was added at Zone 5 at the rate of 53.1 lbs/hr (24.1 kg/hr). Temperature in Zones 4 and 5 was set to 66°C.
• Antioxidant was added to Zone 5 tackifier stream at the rate of .7 lbs/hr (.32 kg/hr).
• the adhesive was applied at a rate of 150 lbs/hr (68.1 kg/hr) and coated to a width of 14 inches (35.6 cm).
• the line speed was automatically adjusted to maintain a coating thickness of 7 mils (177 ⁇ m).
• the adhesive was exposed in line to 1 Mrad of electron beam radiation at 175 kV accelerating voltage.
• Example 2 was repeated except line speed was adjusted to maintain a coating thickness of 13 mils (330 ⁇ m) and electron beam accelerating voltage was increased to 192 kV.
• Example 5 Example 2 was repeated except electron beam dosage was increased to 4Mrads.
• Example 6
• Example 3 was repeated except electron beam dosage was increased to 4MRads.
• Example 7
• Example 6 A similar experiment as Example 6 was run in St. Paul, Minnesota (cool and wet climate) except an additional level of tackifier was evaluated (80 phr) in this full design. Six replicates were run per formulation. After 9 months in this confidential test deck, only two formulations showed zero failure, high tackifier level, high thickness and low cure and low tackifier level (80 phr) low thickness and low cure. Overall 65% of the low cure samples remained down, while only 37% of the high cure samples were present after this time. The ADT was 15,000.

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• 1996
  • 1996-05-24 CA CA2221728A patent/CA2221728C/en not_active Expired - Lifetime
  • 1996-05-24 JP JP50307897A patent/JP3740520B2/ja not_active Expired - Lifetime
  • 1996-05-24 AU AU58790/96A patent/AU704051B2/en not_active Ceased
  • 1996-05-24 DE DE69604290T patent/DE69604290T2/de not_active Expired - Lifetime
  • 1996-05-24 WO PCT/US1996/007760 patent/WO1996041844A1/en active IP Right Grant
  • 1996-05-24 EP EP96920511A patent/EP0830435B1/de not_active Expired - Lifetime

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